"xxx files failed to verify" only means Steam couldn't ascertain whether they were the right versions in the right places---it doesn't mean they're actually not present. A fail will happen if they are missing (obviously) but also if the Steam server and your PC can't communicate 'in a timely fashion' and part of the process times out. Trying to verify at 8pm when everybody hits Twitter/Facebook to comment about Coronation Street is a bad time.....network congestion = high chance of a verify not working y'see.
Have you followed Ruths advice and installed Viual C from the ..\common\Railworks\Install folder? As the error message says "Microsoft Visual C++ Runtime Library" in its top bar gives a clue as to where the problem lies so running the installer should be the first job.
You can enter the editor in S&DJR but not Woodhead; the former is older and much less demanding than the latter so lets just have a look at your resources.
You have 4GB of RAM, which is widely regarded as the bare minimum and as you have a 32 bit OS adding more RAM wouldn't be of use. Have you tried the 3GB switch---http://forums.uktrainsim.com/viewtopic.php?f=361&t=120867
This could just free up enough resources to tip the balance.
The switch relate to VAS, Virtual Address Space which is composed both of real memory and hard drive space, so how much free space do you have on your hard drive?